All of this information is stored in a single table in the database, and there is a single user interface for adding new information. In this way, MusicBrainz has a fairly simple way to deal with extremely complicated data.

The LinkPhrases of the relationships, which describe how to write the relationship information in English sentences.

For example, the advanced relationship type "PerformerRelationshipType" can be used to link an artist (for example, Eric Clapton) to a track on which they performed (for example, Runaway Train). The definition of PerformerRelationshipType allows an optional attribute to specify the instrument he played (InstrumentRelationshipAttribute), so you can say if he played guitar. The definition also says how to construct an English sentence out of this data, so that the website can display the words "Runaway Train was performed by Eric Clapton".

These AdvancedRelationshipTypes are themselves simply entries in another database table. This means that new ones can be defined, old ones deleted, and existing ones modified through a relatively simple user-interface which does not require hacking the database internals. Since this data is much more important than any other individual entries, editing of AdvancedRelationshipTypes is limited to selected users, called RelationshipEditors. There are more relationship editors than developers, and the process of adding a new relationship type is much simpler than adding a new database table, so this is a very fast way to expand and improve the MusicBrainzDatabase.

A list of all of the relationship types defined so far is kept at AdvancedRelationshipTypes. That page also links to documentation for each individual type.

ArtistRoleInheritance

There are now multiple levels at which an artist's role on a song can be recorded: you can relate the artist to the song, to the album, or to the band that recorded the song. So it's now non-trivial to figure out the full list of people who should be credited for any given track.

If the advanced relationship is applicable to all tracks on a release, put it on all the tracks, rather than on the release.

If the advanced relationship is not applicable to all tracks, and you know which ones it applies to, put it on only those tracks.

If the advanced relationship is not applicable to all tracks, and you don't know which ones it applies to, put it at release level. A basic effort to determine to which tracks the relationship is applicable is appreciated, however.

If the credit is release level, and does not apply on a track by track basis (e.g., graphic design for the album's cover), then apply the advanced relationship to the release, not the tracks.

Note: There are still releases that do only have release level advanced relationships, predating the discussions as to where Advanced Relationships should be attached. These still need to be corrected. If you find a release with such release level Advanced Relationships that can be moved to the tracks, please fix them.